"I am very happy about the direction in which the Mac OS X GUI is going, although sadly many Mac users aren't interested in (or don't know about) the "lower levels" of the Macintosh Operating System. Have you ever wondered why the Terminal greets you with the words "Welcome to Darwin"? Why do BSD and Mac OS share certain bits of code? Why does Wikipedia describe Mac OS X as a graphical operating system? Today we're going to take a look at the underlying open source technology which powers your fancy Leopard OS - the hidden core set of components, named Darwin."